Congenital nephrogenic diabetes insipidus (CNDI) is an inborn disorder caused by renal insensitivity to the antidiuretic effects of vasopressin. It is characterized clinically by polyuria, polydipsia, and recurrent dehydration which usually manifest themselves within days or weeks of birth. In some cases, the polyuria and polydipsia can be ameliorated. The goal of this project is to determine the relationships between variations in genotype and clinical phenotype in CNDI.